Update animation classes to use OVERRIDE / FINAL when needed

Source/core/animation/AnimatableLength.h

Index: Source/core/animation/AnimatableLength.h
diff --git a/Source/core/animation/AnimatableLength.h b/Source/core/animation/AnimatableLength.h
index 5ccf934c4b4f6afe3efa3b89c0160eb76d2d9797..bf6433faa053c955649cd4ef5858b20ab18095b2 100644
--- a/Source/core/animation/AnimatableLength.h
+++ b/Source/core/animation/AnimatableLength.h
@@ -46,7 +46,7 @@ enum NumberRange {
 // Handles animation of CSS length and percentage values including CSS calc.
 // See primitiveUnitToNumberType() for the list of supported units.
 // If created from a CSSPrimitiveValue this class will cache it to be returned in toCSSValue().
-class AnimatableLength : public AnimatableValue {
+class AnimatableLength FINAL : public AnimatableValue {
 public:
     enum NumberUnitType {
         UnitTypeCalc,